6:03 a.m.
On 04/10/2013 05:26 AM, Daniel P. Berrange wrote:
On Tue, Apr 09, 2013 at 04:06:06PM -0400, Laine Stump wrote:
> On 04/09/2013 04:58 AM, Daniel P. Berrange wrote:
>> On Mon, Apr 08, 2013 at 03:32:07PM -0400, Laine Stump wrote:
>> Actually I do wonder if we should reprent a PCI root as two
>> <controller> elements, one representing the actual PCI root
>> device, and the other representing the host bridge that is
>> built-in.
>>
>> Also we should use the actual model names, not 'pci-root' or
>> 'pcie-root' but rather i440FX for "pc" machine type, and
whatever
>> the q35 model name is.
>>
>> - One PCI root with built-in PCI bus (ie todays' setup)
>>
>> <controller type="pci-root" index="0">
>> <model name="i440FX"/>
>> </controller>
>> <controller type="pci" index="0"> <!-- Host
bridge -->
>> <address type='pci' domain='0' bus='0'
slot='0''/>
> Isn't this saying that the bridge connects to itself? (since bus 0 is
> this bus)
>
> I understand (again, possibly wrongly) that the builtin PCI bus connects
> to the chipset using its own slot 0 (that's why it's reserved), but
> that's its address on itself. How is this bridge associated with the
> pci-root?
>
> Ah, I *think* I see it - the domain attribute of the pci controller is
> matched to the index of the pci-root controller, correct? But there's
> still something strange about the <address> of the pci controller being
> self-referential.
Yes, the index of the pci-root matches the 'domain' of <address>
Okay, then the way that libvirt differentiates between a pci bridge that
is connected to the root, and one that is connected to a slot of another
bridge is 1) the "bus" attribute of the bridge's <address> matches
the
"index" attribute of the bridge itself, and 2) "slot" is always 0.
Correct?
(The corollary of this is that if slot == 0 and bus != index, or bus ==
index and slot != 0, it is a configuration error).
I'm still unclear on the usefulness of the pci-root controller though -
all the necessary information is contained in the pci controller, except
for the type of root. But in the case of pcie root, I think you're not
allowed to connect a standard bridge to it, only a "dmi-to-pci-bridge"
(i82801b11-bridge)
>> </controller>
>> <interface type='direct'>
>> ...
>> <address type='pci' domain='0' bus='0'
slot='3'/>
>> </controller>
>>
>> - One PCI root with built-in PCI bus and extra PCI bridge
>>
>> <controller type="pci-root" index="0">
>> <model name="i440FX"/>
>> </controller>
>> <controller type="pci" index="0"> <!-- Host
bridge -->
>> <address type='pci' domain='0' bus='0'
slot='0'/>
>> </controller>
>> <controller type="pci" index="1"> <!-- Additional
bridge -->
>> <address type='pci' domain='0' bus='0'
slot='1'/>
>> </controller>
>> <interface type='direct'>
>> ...
>> <address type='pci' domain='0' bus='1'
slot='3'/>
>> </controller>
>>
>> - One PCI root with built-in PCI bus, PCI-E bus and and extra PCI bridge
>> (ie possible q35 setup)
> Why would a q35 machine have an i440FX pci-root?
It shouldn't, that's a typo
>> <controller type="pci-root" index="0">
>> <model name="i440FX"/>
>> </controller>
>> <controller type="pci" index="0"> <!-- Host
bridge -->
>> <address type='pci' domain='0' bus='0'
slot='0'/>
>> </controller>
>> <controller type="pci" index="1"> <!-- Additional
bridge -->
>> <address type='pci' domain='0' bus='0'
slot='1'/>
>> </controller>
>> <controller type="pci" index="1"> <!-- Additional
bridge -->
>> <address type='pci' domain='0' bus='0'
slot='1'/>
>> </controller>
> I think you did a cut-paste here and intended to change something, but
> didn't - those two bridges are identical.
Yep, the slot should be 2 in the second one
>> <interface type='direct'>
>> ...
>> <address type='pci' domain='0' bus='1'
slot='3'/>
>> </controller>
>>
>> So if we later allowed for mutiple PCI roots, then we'd have something
>> like
>>
>> <controller type="pci-root" index="0">
>> <model name="i440FX"/>
>> </controller>
>> <controller type="pci-root" index="1">
>> <model name="i440FX"/>
>> </controller>
>> <controller type="pci" index="0"> <!-- Host
bridge 1 -->
>> <address type='pci' domain='0' bus='0'
slot='0''/>
>> </controller>
>> <controller type="pci" index="0"> <!-- Host
bridge 2 -->
>> <address type='pci' domain='1' bus='0'
slot='0''/>
>> </controller>
>> <interface type='direct'> <!-- NIC on host bridge 2 -->
>> ...
>> <address type='pci' domain='1' bus='0'
slot='3'/>
>> </controller>
>>
>>
>> NB this means that 'index' values can be reused against the
>> <controller>, provided they are setup on different pci-roots.
>>
>>> (also note that it might happen that the bus number in libvirt's config
>>> will correspond to the bus numbering that shows up in the guest OS, but
>>> that will just be a happy coincidence)
>>>
>>> Does this make sense?
>> Yep, I think we're fairly close.
> What about the other types of pci controllers that are used by PCIe? We
> should make sure they fit in this model before we settle on it.
What do they do ?
Although I've asked that question, and had it answered, several times
now, without a tabular list, I'm still unable to get the answer to that
question clear in my mind :-/
Here's the controllers that aw has talked about (in a recent response on
a different sub-thread):
On 04/05/2013 03:26 PM, Alex Williamson wrote:
For PCIe, we create new buses for root ports (ioh3420), upstream
switch
ports (xio3130-upstream), downstream switch ports (xio3130-downstream),
and the dmi-to-pci bridge (i82801b11-bridge). For PCI, PCI-to-PCI
bridges create new buses (pci-bridge and dec-21154).
Alex: what do each of these connect to, and what can be connected to them?
root-port (ioh3420)
upstream-switch-port (xio3130-upstream)
downstream-switch-port (xio3130-downstream)
dmi-to-pci-bridge (i82801b11-bridge)
We already know/understand this one: pci-bridge; is this identical in
behavior/function? dec-21154
One of my goals is to move us away from emulation of specific chips
and
create more devices like pci-bridge that adhere to the standard, but
don't try to emulate a specific device. Then we might have "root-port",
"pcie-upstream-switch-port", "pcie-downstream-switch-port", and
"dmi-to-pci-bridge" (none of these names have been discussed).